This application is a national phase application of International Application No. PCT/GB99/04017, which was filed on Dec. 3, 1999 and which published in English on Jun. 8, 2000, which in turn claims priority from Patent Application No. GB 98 26671.1, which was filed on Dec. 3, 1998.
The present invention concerns a replaceable filter element or cartridge and in particular, though not exclusively, to such an element or cartridge for the filtration and purification of air. The invention also relates to an active device forming part of a pneumatic or vacuum system protected by such a filter. Such active devices include compressors, vacuum pumps, valves and the like.
Broadly stated, the invention provides a fluid filter having a concealed tamper-proof machine-readable identification.
The invention further provides filtration apparatus comprising a fluid filter as aforesaid and a filter head or housing having means for reading or otherwise detecting the identification.
The invention further provides a device or system in which a filter is present for conditioning a flow of gas or liquid to assure the correct functioning of the device or system, in which the filter is required to be replaced periodically, and in which the filter has a machine readable identity which the device or system can read to verify whether a correct filter is in place.
The invention may be provided by an active device having its own power source. However, it is preferred that it should be provided by a passive or un-powered device such as a resonator, memory device or transsponder that can be interrogated by signals from a reader which may be directly connected thereto or may be magnetically or electrostatically coupled thereto.